Counterfeiting and forgeries continue to proliferate. A hot area of counterfeiting is consumer products, such as cellular phones, logos and cameras. Often cellular phones include interchangeable faceplates. (Or a camera includes a logo plate, which is easily replicated by thieves.). A common counterfeiting scenario involves counterfeiting the faceplate, and then passing off the counterfeit faceplate as genuine.
One solution is to provide steganographic auxiliary data in or on consumer products to help prevent or detect counterfeiting. The data can be decoded to determine whether the object is authentic. The auxiliary data may also provide a link to a network resource, such as a web site or data repository. The absence of expected auxiliary data may also provide a clue regarding counterfeiting.
One form of steganography includes digital watermarking. Digital watermarking systems typically have two primary components: an encoder that embeds the watermark in a host media signal, and a decoder (or reader) that detects and reads the embedded watermark from a signal suspected of containing a watermark. The encoder can embed a watermark by altering the host media signal. The decoding component analyzes a suspect signal to detect whether a watermark is present. In applications where the watermark encodes information, the decoder extracts this information from the detected watermark. Data can be communicated to a decoder, e.g., from an optical sensor.
One challenge to the developers of watermark embedding and reading systems is to ensure that the watermark is detectable even if the watermarked media content is transformed in some fashion. The watermark may be corrupted intentionally, so as to bypass its copy protection or anti-counterfeiting functions, or unintentionally through various transformations (e.g., scaling, rotation, translation, etc.) that result from routine manipulation of the content. In the case of watermarked images, such manipulation of the image may distort the watermark pattern embedded in the image.
A watermark can have multiple components, each having different attributes. To name a few, these attributes include function, signal intensity, transform domain of watermark definition (e.g., temporal, spatial, frequency, etc.), location or orientation in host signal, redundancy, level of security (e.g., encrypted or scrambled), etc. The components of the watermark may perform the same or different functions. For example, one component may carry a message, while another component may serve to identify the location or orientation of the watermark. Moreover, different messages may be encoded in different temporal or spatial portions of the host signal, such as different locations in an image or different time frames of audio or video. In some cases, the components are provided through separate watermarks.
There are a variety of alternative embodiments of an embedder and detector. One embodiment of an embedder performs error correction coding of a binary message, and then combines the binary message with a carrier signal to create a component of a watermark signal. It then combines the watermark signal with a host signal. To facilitate detection, it may also add a detection component to form a composite watermark signal having a message and detection component. The message component includes known or signature bits to facilitate detection, and thus, serves a dual function of identifying the mark and conveying a message. The detection component is designed to identify the orientation of the watermark in the combined signal, but may carry an information signal as well. For example, the signal values at selected locations in the detection component can be altered to encode a message.
One embodiment of a detector estimates an initial orientation of a watermark signal in a host signal, and refines the initial orientation to compute a refined orientation. As part of the process of refining the orientation, this detector may compute at least one orientation parameter that increases correlation between the watermark signal and the host signal when the watermark or host signal is adjusted with the refined orientation.
Another detector embodiment computes orientation parameter candidates of a watermark signal in different portions of a signal suspected of including a digital watermark, and compares the similarity of orientation parameter candidates from the different portions. Based on this comparison, it determines which candidates are more likely to correspond to a valid watermark signal.
Yet another detector embodiment estimates orientation of the watermark in a signal suspected of having a watermark. The detector then uses the orientation to extract a measure of the watermark in the suspected signal. It uses the measure of the watermark to assess merits of the estimated orientation. In one implementation, the measure of the watermark is the extent to which message bits read from the target signal match with expected bits. Another measure is the extent to which values of the target signal are consistent with the watermark signal. The measure of the watermark signal provides information about the merits of a given orientation that can be used to find a better estimate of the orientation. Of course other watermark embedder and detectors can be suitably interchanged with some embedding/detecting aspects of the present invention.
Some techniques for embedding and detecting watermarks in media signals are detailed in the assignee's co-pending U.S. patent application Ser. No. 09/503,881, U.S. Pat. No. 6,122,403 and PCT patent application PCT/US02/20832 (published as WO 03/005291), which are each herein incorporated by reference. The artisan is assumed to be familiar with the foregoing prior art.
In the following disclosure it should be understood that references to watermarking and steganographic hiding encompass not only the assignee's technology, but can likewise be practiced with other technologies as well.
Recent developments of highly reflective films and surfaces have required consideration of how best to steganographically mark these types of surfaces. One such surface is a so-called specular surface. A specular surface often reflects light away from the light's source. This can create signal detection problems since relevant optical scan data may be reflected away from a co-located optical sensor.
Accordingly, one aspect of the present invention provides a method of steganographically marking a specular surface. The method includes steps to provide a steganographic signal including at least plural-bit data, and to arrange ink in a pattern on the specular surface to represent the steganographic signal. The ink, once arranged on the specular surface, provides a surface including at least a diffuse reflection property.
Another aspect of the present invention provides a method of marking a specular surface. The method includes the steps of: providing an image including generally uniform pixel values; embedding a digital watermark signal in the image, which effects a change to at least some of the generally uniform pixel values; thresholding the digitally watermarked image; and printing the thresholded, digitally watermarked image on the specular surface with an ink or dye that, once printed, provides an ink or dye surface comprising at least a diffuse reflection property.
Yet another aspect of the present invention is a three-dimensional molded article. The article includes a decorative film or substrate and an adjacent molded polymeric base. The decorative film or substrate includes a specular surface. An improvement to the article is a steganographic signal applied to the decorative film or substrate through arranging an ink pattern on the specular surface. A coloration of the ink is selected to conceal the ink pattern on the specular surface.
Still another aspect of the present invention is a method of steganographically marking a mirror-like surface. The mirror-like surface includes a first coloration and a first finish. The method includes the steps of providing a steganographic signal including at least plural-bit data, and arranging ink in a pattern on the mirror-like surface to represent the steganographic signal. The ink forms a surface which provides Lambertian reflection. At least one of an ink coloration and ink finish is selected to hide the ink with respect to at least one of the first coloration and the first finish.
Yet another aspect of the present invention is a laminate comprising a multi-layered structure including a film having a specular surface. The film is sandwiched between a polymeric substrate and an over-laminate. An improvement to the laminate is ink adjacently arranged to the specular surface so as to convey a steganographic signal. The ink provides an ink surface with a diffuse reflection property.
The foregoing and other features and advantages of the present invention will be even more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. Of course, the drawings are not necessarily presented to scale, but rather focus on inventive aspects of the invention.